Talk:Chobham armour/Archive 1

Archive 1

Pics/Diagrams?

Any pics or diagrams? I'm interested in seeing what this armor looks like/how it works. Maybe an animated GIF of a round penetrating and being deflected/disrupted by the armor? Shrumster 17:02, 30 January 2007 (UTC)

The pictures available are classified and/or copyrighted. The assemblage looks like what it is: a metal framework holding ceramic tiles. When there is a metal face plate, the entire assemblage looks like a metal plate. The heavy armour modules look like removable metal boxes, because they are contained in these. Should you open them, the topology then visible isn't easily described and strongly varies among types. Most published diagrams in the popular literature are rather simplistic and deceptive. Some are downright nonsensical. Especially the terms "layer" and "rod" have confused many artists, apparently not having got a clue how they should be interpreted :o). Anyone is invited to go to http://63.99.108.76/forums/index.php?s=5994548d9d786158a232a99ba6583369&showforum=8 and make a nice drawing of the typical penetration effects, basing himself on the pictures shown in the various pdfs made available through this site. --MWAK 08:35, 31 January 2007 (UTC)

Plastic Armour

Does anyone know if there is a relation to the second world war era Plastic armour, Chobham style armour can't have arrived out of no where and the earlier Plastic armour is similar in concept in being fine but tough granules kept in shape by a matrix. KTo288 13:59, 10 August 2007 (UTC)

It would indeed not be incorrect to say that Chobham is directly derived from development lines started in the forties.--MWAK 17:27, 10 August 2007 (UTC)

Does that double negative mean yes?KTo288 09:58, 11 August 2007 (UTC)

Yes :o).--MWAK 18:24, 11 August 2007 (UTC)

ThanksKTo288 21:02, 11 August 2007 (UTC)

Further work

No thanks. I'll continue being diligent by first of all adding the references you indicated as the most necessary :o). Your restructuring of the article is very reasonable; only I feel that it would be more "logical" to first give the general physical principles involved — in an expanded section — and only then present the structural properties. I'll also try and create a short "Development" section, as an introduction to the subject.--MWAK 10:56, 29 August 2007 (UTC)

"No thanks"?

I'm not sure that we can get away with explaining the protection factor first, again due to the angle of not trying to teach content. We should first describe, then explain things, rather than presenting the problem first. But no reason not to experiment!

The article's looking pretty nice now. Once it's got more inline citations, it can probably get graded as a good article. Chris Cunningham 12:01, 29 August 2007 (UTC)

Sorry, I didn't mean "No, thanks" but "No thanks are necessary". My germanic background got the better of me...I indeed have taught this subject in the past, so that could explain my educational approach of the matter :o).--MWAK 19:09, 29 August 2007 (UTC)

Reference formatting

Okay, we've got a lot of contextual referencing now. We should move to eliminating redundancy by having a References section containing the full description of the books being referenced (in proper cite tags) and a Footnotes section which contains the page numbers. I'll start doing this. Chris Cunningham 07:56, 4 September 2007 (UTC)

Very good idea! Thank you for your efforts; I myself tend to be a bit lazy and simply copy the whole for each footnote...--MWAK 07:13, 6 September 2007 (UTC)

Leopard 1 "glacis armour"

Such modules are also used by tanks not equipped with Chobham armour; an early less sophisticated steel version of such armour can be seen attached to the glacis of the German Leopard 1.

I'm removing this, until someone can find a reference. As far as I know, the only thing which can be seen attached to the Leopard's glacis is the metal racks for storing the track grousers, seen empty and loaded in the photos here.

I sure hope the article isn't full of other such tidbits. —Michael Z. 2007-10-03 22:58 Z

Yes, but the reason the track grousers have the shape they do and are attached at this particular place is that they can function as a primitive perforated armour system :o).--MWAK 07:42, 4 October 2007 (UTC)

Chapter: "Effectiveness"..

Everything writen under here is false. 1st, armored vehicles and MBT's were lost in both 91 and 03 and to ATGM's, ROCKETs and Grenades and KE-weapons, including M1's and Challengers. Also this story about the punctured sideskirt M1 is bogus too, it was no tandem warhead, just your common PG-7VL or VM, and this with 330 -> 550 RHA penetration is far cry from the PG-7VR of which none of have ever been encountered in Iraq, infact only know use of this round has been from Checnya and even from there theres been just few photos of this in use.

Well, it's not the best section of the article ;o). The main point however is this: no existing RPG can easily penetrate the Chobham armour proper, i.e. the ceramic tiles. The silicon carbide composite used has a mass efficiency of over 25. A typical double layer configuration would have the equivalence of about 1000 RHA against hollow charges. A RPG-7, whether it has a tandem warhead or not (no, it will not "pre-shatter" the tile), will probably not penetrate even a single layer. But only a part of the vehicle is protected by Chobham.--MWAK 12:23, 11 November 2006 (UTC)

• Only 1 Challenger2 has been destroyed......It was a "blue on blue" incident. —Preceding unsigned comment added by 86.129.37.181 (talk) 16:18, 8 October 2007 (UTC)

Why an M1 Picture?

Since this is British armour I don't think that the only picture should be of an American tank! Why don't we put a picture of a Challenger 2 up there? —Preceding unsigned comment added by TechnoRat (talk • contribs) 17:26, 24 January 2008 (UTC)

Make that a Challenger 1, I would say :o). But again: it has become a generic name.--MWAK (talk) 08:08, 26 January 2008 (UTC)

Done. --Padijow (talk) 22:21, 13 May 2008 (UTC)

"Structure" versus "Protective qualities" again

The more I look at this, the more I think that we should be explaining what the armour does before how it does it. I really think the order of these sections would be best swapped. Chris Cunningham (not at work) - talk 23:23, 11 October 2008 (UTC)

Yes, one of the many possible logical orders could be to first discuss the demand made on such armour, then the general qualities which enable it to meet this demand, followed by the consequences for auxiliary structures and finally the way all the components fit together to form a coherent whole.--MWAK (talk) 07:14, 12 October 2008 (UTC)

Time to propose GA?

Article looks pretty nice now, informative and complete. Think it's time to nominate it as a good article? Chris Cunningham (not at work) - talk 12:44, 13 October 2008 (UTC)

Well, it is informative, but complete? As someone probably having an above average knowledge of the subject, I'd say there are many, many gaps: the Start-class criterion "The article has a meaningful amount of good content, but it is still weak in many areas" is still applicable. The history section is somewhat adequate, but the technical sections are very superficial; they really form but the roughest outline of the content that should be there. Also, obviously, any serious quantification of the main physical principles and material properties involved is simply lacking. If Wikipedia is to be taken seriously we had better abstain from puting the label "good" on texts that any expert would consider simplistic or even childish...Maybe we could uprate it to the new C-class instead? ;o)--MWAK (talk) 08:10, 14 October 2008 (UTC)

Fancy posting an outline of where you think it should be headed, content-wise? Chris Cunningham (not at work) - talk 13:06, 14 October 2008 (UTC)

As said, the present text already is an outline! The desired content is indicated by the implied questions posed by it. If we read the first sentence of the Protective Qualities chapter: "Due to the extreme hardness of the ceramics used, they offer superior resistance against a shaped charge jet and they shatter kinetic energy penetrators (KE-penetrators)", we ask ourselves: "How extreme is that hardness? Are some ceramics harder than others? Is there a hardness variation within a ceramic and would this matter? How superior is their resistance exactly? Superior compared to what? How does it vary with the hardness? Is the same mechanism used to shatter those penetrators? Are jets and penetrators equally affected? Are all jets or penetrators equally affected? What is the relation with toughness? With density? With temperature?" etc., etc.--MWAK (talk) 07:08, 15 October 2008 (UTC)

An error?

" The effectiveness of Chobham armour was demonstrated in the first Gulf War, where no Coalition tank was destroyed by the obsolete Iraqi armor. "

I know this does not make sense, and I can think of no appropiate word to replace the second 'armour'. Perhaps someone would like to fix?

It sounds a bit silly :o). "Tanks" might well do.--MWAK 08:09, 7 February 2006 (UTC)

Or "ordnance". Gdr 22:22, 7 February 2006 (UTC)

"armor" is sometimes used as a shortened form of "mobile armor" (which is to say, tanks or other armored fighting vehicles). Here it is clear that the author meant Iraqi tanks. TTK 05:55, 8 March 2006 (UTC)

I forgot to thank you, once I discovered your contribution here, for the enormous amount of work you have done in the past to make available information about this subject to the larger public!--MWAK 20:42, 11 May 2006 (UTC)

One could also say "obsolete Iraqi AFVs" (for Armored Fighting Vehicle) or "fighting vehicles", or "landcruisers" (which would be a rather dated and British term) or simply list the nomenclature of the Iraqi armor involved. —Preceding unsigned comment added by Woerkilt (talk • contribs) 04:51, 27 February 2009 (UTC)

Effect of sloped armor

The article seems to operate on the assumption that the only advantage to sloped armor is the chance of deflection. That's not the primary advantage. The advantage is simply that the steeper the angle of the hit, the more metal a penetrator has to through in order to breach the armor. As a rule of thumb, every 30 degrees off the perpendicular effectively doubles the amount of armor that has to be penetrated. And so while having flat-sided armor may be an advantage against HEAT rounds, it's a significant disadvantage against kinetic penetrators.

Well — aside from your rule of thumb, which is simply incorrect — you make the common mistake to forget that although angling implies that a longer stretch of armour has to be penetrated, this offers no weight advantage, simply because the angled armour plate has to be proportionally longer. See sloped armour.--MWAK 05:46, 24 September 2006 (UTC)

As applied to most armoured vehicle design below Main Battle Tank level the sloping of the armour is usually applied in conjunction with reducing the thickness of the metal so as to provide the same protection at lower weight with the primary objective of improving performance and mobility; this was a feature of the German half tracks of WWII from which all modern light armoured fighting vehicles have been developed today. The effectiveness of their light armour and greater mobility compared with that of Allied types at the time was profound. Whilst sloped armour can provide some deflection properties these are slight at best. Where deflection does occur against armour it is mostly due to the projectiles own energy being transformed by its momentum in finding its path blocked by impenetrable armour, the unspent energy has to go somewhere.86.27.129.157 (talk) 22:32, 11 October 2008 (UTC)

No, you are mistaken: the benefit of sloping resides in two mechanisms: a better weight efficiency in enveloping the armour and deflection effects. "Reducing the thickness of the metal so as to provide the same protection at lower weight" does not work as such, because, as I stated above, the plate has to be proportionally longer. As it happens, the deflection effects are relatively larger for lighter projectiles, and therefore more relevant for light AFVs. The superiority of German light armour in some phases of the Second World War was due to a more effective tactical and operational use, not to their sloped armour array, as the opposing armies also applied the principle extensively in their vehicle design.--MWAK (talk) 13:31, 27 February 2009 (UTC)

Protection Levels?

So what are the actual protection statistics for the Chobham armor? I mean, how much RHA protection would 100mm of Chobham armor equal?--HellraizerofUSA (talk) 22:35, 29 June 2009 (UTC)

Well, there is no such thing as the Chobham armour. Types vary a lot. Also the threat varies a lot: KE is different from HEAT-attack. And then there is the problem of the interaction between the different components: ceramics, foam, metal backing plates. Pure ceramic armour from the seventies would, for a given weight, be a few times more effective against HEAT-attack than RHA. As it was also a few times lighter, for a given thickness the protection would be about equal. Against KE-attack the effectiveness would have been about equal for the same weight, meaning it would be a few times less for a given thickness.

A modern ceramic would be expected to have a protection level against HEAT that is a full order of magnitude better. That means that even a plate of the same thickness would be about ten times as effective than RHA. But its protective qualities as regards KE have not kept up, meaning it would give about the same protection against penetrators as a RHA-plate of the same thickness.--MWAK (talk) 07:21, 30 June 2009 (UTC)

Citatation needed on hardness being primary factor in defeating shaped charge jets

As pretty much all materials can be treated as a liquid when hit at the speed a shaped charge jet moves (see page on shaped charge) at I don't see how hardness could help. —Preceding unsigned comment added by 188.221.161.189 (talk) 18:31, 31 January 2010 (UTC)

Yes, pretty much all materials. This is why only certain materials are useful for "special" armour :o). The main mechanism, as explained in the text, is that the armour is brittle and fractures, the "shards" destroying the geometry of the "jet". You cannot use hydrodynamics to correctly describe the process. It's a bit more chaotic, so to say.--MWAK (talk) 14:48, 1 February 2010 (UTC)

Hydrodynamic models (models which treat penetrator and target materials as liquids) were the best people could come up with to describe hypervelocity-domain penetration in the 1960's, but we've learned a lot about it since then. The interacting materials are not literally liquids. Characteristics such as hardness, elasticity, and material strength play a significant role in the behavior of hypervelocity penetrations, as evidenced by Anderson's, Lanz's, and Odermatt's recent contributions to the field. Now, that having been said, calling hardness "the primary factor in defeating shaped charge jets" seems like an overstatement, or perhaps a misrepresentation of "surface dwell" (also known as "interface defeat", where penetrator material moves laterally across the face of hard ceramic components for a relatively long time before penetrating into the ceramic). If dwell plays a primary role in Chobham/Burlington's operation, then the claim would be more understandable (though still worded a bit poorly). Producing dwell depends on a number of factors: (1) a ceramic material with high compressive strength, (2) a high quality of bond between the ceramic component and a hard, strong, dense backing component (such as steel, tungsten heavy alloy, or depleted uranium alloy), and (3) hydrostatic prestressing of the ceramic component. Lacking any one of these things will greatly diminish the surface dwell. TTK (talk) 18:19, 3 June 2010 (UTC)

Chobham armour

I have a really hard time believing the describtion of Chobham armour function's against hollow shaped charge weapons. I don't really see how "Hardness", "cracking" or "ragged entrance channel" has much to do with stopping a jet of very hot molten metal. Not being a expert in materials, I would presume that any material coming into contact with such a hot jet and thus subjected to extreame temperatures and pressures, will simply melt or even vaporise (mostly as grains). (And thus it loosses it's structual brittleness and hardness, though the individual grains keeps the hardness). My - lay man's - Understanding of Chobham, armour is that it works like reactive armour: You have a sandwich structure of two plates with a ceramic in between. When the outer plate is hit and penetration begins, energi is transfered through the outer plate and to the ceramic in form of high pressure. Because the ceramic is confined (by the outer and inner plate) the pressure result in a steep temperature increase which more or less vaporises the ceramic, creating a gas under high pressure consisting of grains of the ceramic. When the molten jet, of the shaped charge, burns through the outer plate it so to speak "punctures the baloon", and the high pressurised gas (of the ceramic material) shoots out, directly against the direction of the molten jet. This causes the molten jet to loose momentum and de-focusses the jet. This also explains why chobaham is more effective against HEAT than Ke penetrators, since while the reactive effect does, I presume, significantly decrease the momentum of the penetrating rod (f.ex. by abrading it, I suspect) it can't "de-focuss" it or, more relevant, make it change direction (because the reaction "jet" and the rod moved in more or less exact opposite directions).

I suspect that if you want to use hardness (to shatter the penetrator) or cracking (to divert energy laterally) you would want to have the penetrator make a clean hit on that material, not allow the penetrator to "prime" that material by heating (which makes the material more soft and less brittle) as it strikes through outer layers on it's way through the entire armour package. Jomsviking (talk) 11:49, 3 January 2011 (UTC)

Well, you have become the victim of simplified accounts in popular books about the functioning of hollow charge weapons. Contrary to what is commonly stated there, the explosion by a hollow charge does not form a "jet of molten metal". Yes, there is a jet, but of hot gasses. And there is metal but not in a real jet nor is it molten. The explosion force compresses the soft metal covering ("liner") of the hollow cone and deforms it. This happens so quickly that it simply hasn't got the time to melt. Instead a "hypertensile" stretched metal string is formed. The penetrative qualities of this object largely depend on its speed and mass, not on its temperature. Basically it is just a KE-penetrator but with a very high speed (the tip would leave the planet if not for the atmosphere), a rather low mass and very little cohesion because it is in an immediate process of disintegration. The latter is its Achilles heel, exploited by ceramic armour. And no, also the gasses do not sufficiently vaporise the ceramic for a "balloon" to be formed — although they contribute to the velocity of ceramic particles that break the "jet" geometry. These particles are not the "grains" of a gas: a gas has per definition no grains and if the gas pressure would be directly effective it would not matter much whether it had been made from metallic or other molecules and ceramic armour would offer no advantages over steel. However, the main mechanism is simply that the penetrator follows the path of least resistance, being the rather chaotic cracks in the ceramic.--MWAK (talk) 20:36, 3 January 2011 (UTC)

You have to cut me some slack in the prober use of technical terms in english, what little material physic I was thought a long time ago was in a different lanquage.

I accept your better describtion of a shaped charge. Though as far as I can see it doesn't really make a difference in respect to what I am trying to say.

I apologize for the confusion created by me using the word "gas", maybe a "dust cloud made up of tiny grains/pieces of the ceramic" would have been better?

"However, the main mechanism is simply that the penetrator follows the path of least resistance"

That's a new mechanical principle for me; So we have a jet of hot gasses; plz explain how these molecules/particles change their momentum to magically follow the path of least resistance? (the "jet" would probably propagate longest along the path of least resistance, but that doesn't mean that it follows the path of least resistance)

"it would not matter much whether it had been made from metallic of other molecules and ceramic armour would offer no advantages over steel."

Let's take the "dust cloud" picture instead of a "gas", the difference would f.ex be the hardness of the grains/tiny pieces of the ceramic and the high melting point (preventing the transition into a proper gas). But ofcourse if chobham armour doesn't work this way, it's irrelevant. Though you do write; "although they contribute to the velocity of ceramic particles that break the "jet" geometry."

You mean that particles are moving freely? If particles are moving freely, one would suspect that the moment the "jet" get into contact with such a medium of moving particles, it will be bombarded by them (because of the high velocities involved, because temperature is high), which as you say "break the "jet" geometry.", or as I like to put it; defocuss it and results in the "jet" dissipating in a larger volume of material - and thus loosing it's penetrating power.

Which is exactly what I stated in my opening post;

" I don't really see how "Hardness", "cracking" or "ragged entrance channel" has much to do with stopping a jet of very hot molten metal." (where "hot molten", should have been "hot gaseous" or something)Jomsviking (talk) 22:46, 3 January 2011 (UTC)

I fear I've been not sufficiently clear. Yes, we do have a jet of hot gasses but this real jet is of minor importance. Let's forget about them for a moment and concentrate on the main mechanism. The penetration is largely effected by the "sting" of hypertensile metal. This sting is not gaseous nor a fluid but a solid in a process of extreme deformation. When its tip impacts the tile surface it will cause the ceramic to crack at that point. This is why hardness and brittleness are essential: a too soft or too tough material will not crack. The cracks will not nicely follow the ballistic trajectory of the sting but form at an oblique angle. This means the tip of the sting will now encounter an oblique surface and will be deflected in the direction of the crack, hit more ceramic nevertheless causing more cracks, etc., etc. until it is defeated. At first the incoming broader parts of the sting will be forceful enough to create a more or less straight entrance channel anyway but its ragged sides will nevertheless keep obstructing and deflecting the subsequent even broader parts of the sting, a process enhanced by (preferably large, not small) pieces of the ceramic of the channel wall breaking off. So that is also part of the defocusing. The later, much slower, sting parts will not find a nice small entrance hole at the end, formed by the tip, as when steel armour is hit. Instead they will encounter a heap of ceramic rubble. When the tile is thick enough during the last phase the remaining metal, the back of the "carrot", will "mushroom" sideways. So, a lot of culinary similes there: I hope the explanation is edible ;o).--MWAK (talk) 08:54, 4 January 2011 (UTC)

I think you have desribed to me some basics about how ceramic armour diverts energy and momentum laterally. And I think it sounds reasonable. Though I find it hard to believe that the famed Chobham armour, that revolutionized (then) modern tank warfare, a great secret of the western world and one of "our" then best cards in offsetting the numerical superiority of the warsaw pact armoured forces, was "simply" a question of producing and manufacturing a ceramic like Titanium diboride (or other ceramics like that) in a tile (matrix of some material, what ever) and utilizing it's (inherrent) material properties. I would suspect that the "communists" would have caught up to that idea pretty fast. I suspect that (or reason dictates) that there has be something subtible, something that aren't or weren't more or less common (for specialists) ceramic knowledge at the time - but ofcourse that's a secondary argument. Jomsviking (talk) 11:25, 4 January 2011 (UTC)

also, but that's just pure speculation from my part, I am puzzeled why a high momentum impact in a very short time, simply doesn't shatter the ceramic (which as far as I know is quite stiff) into a fine powder (kinda like hitting burnt clay with a hammer), in which case the crystaline/structual properties (lack the correct word) you describe is irrelevant Jomsviking (talk) 11:39, 4 January 2011 (UTC).

Well, the reason why this technological development eventually was advantageous to the West was precisely that the Soviets had a head start. Being the first to implement a cheap version, induced them to start mass production of too light types, in the 40 ton class. But you need a 55 ton vehicle to really benefit from these systems. I have no doubt that if the tile system was not invented by them in the first place (you never know), it was certainly known to them shortly after its conception. So, it was not The Great Secret nor strictly necessary to offset the numerical disparity which was not all that extreme to begin with. I strongly suspect that the mystique surrounding Chobham stemmed from people despairing of explaining terms like "hypertensile" ;o).

Regarding "shattering" versus "cracking": the difference is gradual. But the comparison with a hammer is very informative. I knew a ATGW-instructor once who tried to boost the morale of his TOW-teams by showing them that ceramic armour was far from invincible. He had a whole supply of old alumina tiles from the Americans and at the beginning of the lesson he showed one to his audience, explaining it was an advanced ultra-secret material providing superior protection. Then he lifted a normal hammer to hit it with. The men of course expected it would simply bounce off without even a scratch being made. Every time they gasped with surprise when he easily shattered the outside and whole chunks flew off. Ceramics are vulnerable to rather slow impacts with heavy masses. The hollow charge "sting" is to the contrary very fast and very light. "Momentum" has two component factors; its all depends which is the dominant one, speed or mass.--MWAK (talk) 17:13, 4 January 2011 (UTC)

""Momentum" has two component factors; its all depends which is the dominant one, speed or mass."

Exactly; you have lowish mass, but very high velocity, which translates into a high momentum. The derivative (rate of change) of the momentum with respect to time is the force (or the momentum is the integral of the force wrt time), hence if the change in momentum is large wrt time, then the exerted force will be large. In this case we have a high speed "collision" that is over in a very short time, hence the rate of change of the momentum (the derivative wrt time) is huge and the force exerted (or rather the force necessary to bring about the (rapid) change in momentum in the given timespan) will be huge, this force is the (oppossed) force that will be used deform the material. But when "enough is enough": at which force a significant part of the ceramic is shattered into powder, I don't know Jomsviking (talk) 20:06, 4 January 2011 (UTC).

Indeed, the kinetic energy depends on the time period and thus can be expressed as ½mv². So, in principle the penetration increases with the square of the velocity. Obviously, there is a modicum of pulverisation at the impact point, but that point is very narrow limiting the amount pulverised. So the front of the sting which is best suited to cause a deep penetration because of its very high speed and high concentration, is the part confronted with the highest relative cracking. The parts arriving later relatively pulverise more material while widening the entrance channel but are slower and broader and thus would have contributed less to the penetration anyway.--MWAK (talk) 07:22, 6 January 2011 (UTC)

Just some physics; The energy is less interesting in the describtion of the collision. The see that, imagine two car accidents; Identical cars speeds at 100Km/h against a concrete wall. The first car hits the wall at 100km/h while the second car breaks down to 50 km/h before it hits the wall. Both cars are brought to a complete stand still in the collision. Now the driver in the first car is toast, but the driver in the secondcar, given seat belt and modern car, will get away from this with minior injuries. Now the "before and after" momentum and the "before and after" energy are the same in the two situations, and the work done on each car is the same. But the force excerted is not the same in the two situations. The guy and car that hit's the wall with 100 km/h is beaten into a pulp by a huge force, while the other guy experiences a much more moderate force (though, in a longer time). It's the force that "breaks" things, (very)coarsely speaking it's the mass times the time interval times the (de)acceleration that causes the damage. In our ceramic it will be the force of the impact that shatters the ceramic first of all, along it's grain boundaries. The force is related to impuls/momentum by the integral of force (it's much harder to derive the force from the energy) Jomsviking (talk) 09:28, 7 January 2011 (UTC).

Anyway, I lack the knowledge, though I am very surprised that "cracking" can make such a difference, since I would believe that the principle manner of penetration is by the "sting" pulverising the ceramic as it goes along (and hence there is nothing to "crack") Jomsviking (talk) 09:28, 7 January 2011 (UTC).

If the warhead is powerful enough and penetration succeeds, that is what will happen of course :o). To understand the defeat mechanism better one should also consider another factor: dwell. The metal of the sting point is slowed when it impacts the tile face. But the shock waves this causes are not and crack the ceramic well in front of it and also in a more lateral direction.--MWAK (talk) 09:26, 8 January 2011 (UTC)

Perforated Armour

Can someone provide some information on what "perforated armour" is? I did a quick search and found nothing particularly enlightening. Currently the link just redirects to the vehicle armour page, which has no mention of it. Bobbis 16:48, 21 Apr 2005 (UTC)

Well, in fact it has :o). But to state the obvious: perforated armour is just that: armour with perforations. To understand the principle applied in its simplest form, imagine a block of steel with perpendicular holes drilled into it, that are smaller in diameter than the penetrator hitting it. If the penetrator hits the area between the holes it has to penetrate the whole of the thickness of the plate - that plate of course being a lot thicker for the same weight now that it has perforations in it. If it hits the edge of the perforation the penetrator will tip, deform or (hopefully) snap. That's one penetrator that won't penetrate. If it snags into the perforation the abrasion will be terrible. And abrasion provides 60% of the protective qualities of any armour even during a normal impact.

Instead of drilling holes into a steel plate you can create a similar structure with perpendicular uranium or tungsten rods, bundled together. Cold tungsten is rather brittle so you'd have to encase it in e.g. titanium tubes.

This is only the principle at its most simple. The protective qualities can be significantly improved by applying materials of different hardness and toughness and by using an advanced topology optimised for the expected penetrator. A remarkable advantage of perforated armour compared to Chobham armour is its vastly superior "multiple hit capability" (i.e. sustainability). When modern perforated armour is hit there's at first a build-up of protection: the addition to the protective mass by the deformed penetrators is at first more important than the loss of structural cohesion! If you keep hitting a Leopard 2A4's frontal armour with a T-80 you'll run out of sabot rounds long before the Leo 2 is knocked out. That's very satisfying from the point of view of the Leopard 2 crew. However if an original M1 was hit by a T-64, after the second hit on the same module its crew was (un)protected by a heap of expensive rubble, only good to make toothpaste from (it's the same stuff).

Perforated armour can also be used to protect LAV's against bullets, but then the thin armour plates have to be really optimised for the bullet calibre.

--MWAK 15:51, 24 Apr 2005 (UTC)

This sounds very much like "spaced armor" from the 1960s, actually.

Indeed such systems were then in development and the principles were implemented in the Leopard 1A3 and A4, the A1A1 in the Mittel and Schwer configuration, as well as the French AMX-32 and 40. These types were therefore much better protected than is often assumed (well, their turrets...). Much what has been described as "spaced" is not of a simple laminate type as would be suggested. --MWAK 09:56, 4 December 2005 (UTC)

http://www.ciar.org/ttk/mbt/papers/ijie01/ijie_25_423.pdf is an interesting paper that looks at the effect of projectiles striking the edge of armour plates. MWAK do you have any references discussing the build-up effect or the composition of Chobham? It might be nice to add a perforated Armour article, or at least add something to Vehicle armour Megapixie 03:56, 13 July 2005 (UTC)

There are no unclassified papers on the build-up phemomenon (which is a freak effect anyway); so it's better not to put it in the article :o). The International Journal of Impact Engineering is an excellent source in general. Also the American Ceramics Society (it sounds so innocent doesn't it? But it isn't all about pottery ;o) can give a lot of information. See e.g. http://www.ceramics.org/meetings/cocoabeach2004/armor.asp. Relevant to the article is especially this abstract:

The drive to develop armor systems for combat vehicles requires improvements in the bonding of ceramic armor to metallic substructures. Current methods that utilize epoxy adhesives provide limited strength and ballistic performance. Reactive multilayer joining offers the novel ability to form strong metallic joints between ceramic tiles and metallic plates at room temperature. Reactive NanoTechnologies’ novel joining technology is based on the use of reactive multilayer foils as local heat sources. The foils are a new class of nano-engineered materials, in which self-propagating exothermic reactions can be initiated at room temperature with a spark, laser or hot filament. By inserting a multilayer foil between two solder or braze layers and two components, heat generated by the reaction in the foil melts the solder and consequently bonds the components. The joining process can be completed in air, argon or vacuum in approximately one second. The use of reactive foils as a local heat source for soldering or brazing eliminates the need for furnaces, speeds up the joining process, and dramatically reduces the total heat that is needed. Most importantly the limited heating of the components virtually eliminates the mismatch in thermal contraction that normally occurs on cooling from soldering or brazing temperatures. Thus large thermal stresses are avoided and large area samples can be bonded. This presentation will begin with a description of the multilayer foils and their use as local heat sources in soldering and brazing. We will then demonstrate their utility in the bonding of two ceramic armor systems, Al2O3/Al and SiC/Ti 6-4. For each of these systems we will first show numerical predictions and IR measurements of heat [t]ransfer. Then we will present shear strength measurements for the joints. The strengths achieved range from 30 to 80 MPa, and are limited by failure in the braze or solder. Finally examples of large scale reactive joints for each of these material combinations will be shown.

It's a public secret that in the late seventies the British used boron carbide and the Americans alumina. Stone age technology by today's standards of course :o). The last ten years, in a desperate effort to lower costs enough to equip even LAV's with an effective protection against RPG's, the USA has tried to mobilise the world's research sources. This could only be done by being less strict about security. Especially through the SBIR-program much has been revealed, among which the fact that silicon carbide is used in vehicle armour. http://www.dtic.mil/matris/sbir/ should be most interesting! Particularly http://www.dtic.mil/dticasd/sbir/sbir012/sba39.html

Should you doubt the claims in the article about recent protection levels: see http://www.fprado.com/armorsite/US-Field-Manuals/abrams-oif.pdf on page 7.

--MWAK 09:11, 13 July 2005 (UTC)

All good stuff.

I've seen some estimates of the M1's protection levels on a couple of forums

• http://img140.echo.cx/img140/2614/untitled52xh.jpg
• http://img140.echo.cx/img140/6391/untitled79fc.jpg
• http://www2.beareyes.com.cn/jpic/1/2005/06/20050604_214800_1.jpg

But a Chinese webpage isn't exactly the most reliable of sources.

The pages on armour are very fragmented (no pun intended). I thought it might be good to re-structure some of it - i.e. a page on each armour type and a main page with summaries linking off to the other pages. The problem is that it's hard to get a concrete references. I'm currently getting side tracked working on Soviet and early western ATGM's - see AT-3 Sagger,Entac ....

Do you think it would be worthwhile re-organising the pages? It's probably going to take me a couple of weeks at least to finish up the ATGM's - but after that I wouldn't mind helping out.

Megapixie 12:44, 14 July 2005 (UTC)

Allow me to comment. :o)

1. The first diagram has the principle right: the original M1 armour consisted of three main sections: an outer thinner steel plate; a thicker steel back plate — and in between the alumina (Al2O3). However it pretends to give exact numbers. It fails because it is based on a complete misunderstanding of CMC's. It shows no matrix, no vibration absorber, no oxygen absorber and no expansion space. In fact it reminds me of nothing so much as Wilkins original work of over forty years ago, as if all you needed was some massive Magical Crystal. Such a configuration would literally self-destruct. It also fails to understand the fundamentally modular nature of the system.
2. The first column of armour equivalence estimates is correct. No wonder: it's the official one. The numbers for the M1A1 and M1A2 are ridiculous underestimations though, unless those of the M1A1 are interpreted as indicating the equivalence of a double silicon carbide matrix, without uranium module. Then you would have a lot of empty space left; a single matrix has a thickness, according to the original SBIR discussion (later partially deleted in the archives :o), of four centimetres. The numbers in the Team Abrams presentation are inches, not feet: a RPG with a nominal penetration of 360 mm steel caused only a hole of about 30 mm deep! Such is the superior quality of the American "eumorphed" silicon carbide composites, so much better than the industrial-grade junk Soviet engineers had to work with. There should be space enough to protect the tank with an equivalence of over a metre against KE and almost double that against HEAT and still remain within a weight limit ensuring 80% reliability (if you have a good maintenance team). Newer composites are in development improving toughness through the use of nanotubes; these should make it possible for the CMC's to really contribute to KE-protection. At present no actually bought KE-rounds can penetrate the M1's frontal armour in its heavy configuration.
3. However, as said, the system is modular; it's up to the theatre commander to decide what the general threat level is, whether strategic mobility demands outweigh the need for protection. I've been told base commanders often remove the CMC's completely to reduce costs by putting them in protected storage, at the same time reducing general maintenance and fuel use. This would then be the origin of the story that the tank "rings hollow" if hit with a hammer. Certainly it seems to be the cause of the heavy suspension damage during the Iraq invasion; drivers made jumps that would have caused no trouble for the unloaded vehicles they were used to, but now destroyed the suspension elements.
4. Speaking about ATGW's (nice work you've done!), it should be noted that the penetration of a hollow charge does in fact not scale linearly with its diameter: heavy missiles are a lot more dangerous than is often presumed. So that's the bad news. :o)

And now about the article structure. As it is now, it isn't too bad. Vehicle armour can be used as a sort of general introduction — and we need one, I feel: remember that for most people, especially those of the female persuasion, all this is completely new and utterly confusing. It would indeed be very nice to have a special "Perforated armour" article; but, as you said, it's hard to get good references and it might be harder still to defend the validity of the article if challenged. As it is a subject people have strong opinions about (to say the least :o) perhaps it should be mentioned only in the context of Chobham. For "normal" steel armour we could use RHA and sloped armour. I often get the impression less attention should be given to all kinds of modern developments and more to the basics of ballistical protection, which the average tank enthusiast doesn't seem to understand at all :o).

--MWAK 15:14, 14 July 2005 (UTC)

On closer inspection I believe the Chinese table is an incorrect copy of a more original one with four columns, the second then giving data for the M1 Improved. This seems to be indicated by the wrong number for the weight increase. Many other data would make more sense if seen as estimates comparing the M1 Imp to the M1A1, rather than the M1A1 to the M1A2. It's also notable it's assumed the replacement ceramic is titaniumdiboride, apparently inspired by reports about the LAV-programme in the mid-eighties. It's certain titaniumdiboride modules were made, but their very high cost makes it doubtful the entire M1-fleet was refitted with them.--MWAK 18:11, 14 July 2005 (UTC)

Absolutely no scientific reasoning behind this article. Oh, and non of the M1 variants use Chobham as this is a British invention which has never been made available to them.

Is there not even a tiny bit of scientific reasoning present? ;>) Regarding your second claim: it all depends on what you call "Chobham". Since the early seventies there has been close cooperation between the British and the Americans in this field.--MWAK 09:35, 26 April 2007 (UTC)

A person sent to me an e-mail, some years ago, that perfurated armour is did as a lot of holes obliquos in the armour.Then comes another plate, without any holes.Being "/" a hole and a "*" normal material, a perfurated armour is such as this: */*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*Agre22 (talk) 13:14, 26 August 2008 (UTC)agre22

Well, in your diagram, the plates themselves are oblique (possible, but not relevant to the principle), not the holes. Also, if you let one plate cover the holes of the other, it would be benificial to have holes in that plate too, just in another position.--MWAK (talk) 06:21, 27 August 2008 (UTC)

Removed last paragraph under 'applications', I have never read such rubbish based on OR, the French followed the British and use a titanium-tungsten system, Dorchester Armour isn't being 'fazed out' if anything the opposite, armies around the world have rushed out to copy it, as an example the Germans and French have dropped spaced armour in favour of the above. Finally to top it off not a single citation either. Why someone would come onto the Chobham Armour entry and push 1960's spaced armour is beyond me and has no place in this article. Twobells (talk) 14:14, 29 June 2012 (UTC)

Development and application section

What a bunch of nonsense, the development of the Leopard 2 armour has no place in the article. It is almost as though whoever wrote it was trying to make some sort of apology/comparison and why on earth is there any mention of GIAT? Twobells (talk) 15:14, 29 June 2012 (UTC)

Well, I can refer to the second line of the intro: "The name has since become the common generic term for ceramic vehicle armour". So, very strictly limiting the scope of the article to the British research and its direct American offshoots is unwarranted. Therefore it is relevant to indeed make a comparison with the systems of other nations, including one from GIAT.--MWAK (talk) 05:54, 30 June 2012 (UTC)

infobox

there must be some kind of infobox we could add? maybe including users, year, manufacturers ect. (Fdsdh1 (talk) 20:31, 15 November 2012 (UTC))

Well, infoboxes must use some standardised format. I don't think a standard box is available that is applicable here.--MWAK (talk) 06:30, 16 November 2012 (UTC)